Curable epoxy resin compositions that contain thermally conductive fillers and that are used as adhesives and sealants capable of efficiently transmitting heat generated by electronic devices are known in the art. In general, curable epoxy resin compositions produce cured products having a high modulus of elasticity and, therefore, high rigidity. As disclosed in Japanese Unexamined Patent Application Publication (hereinafter referred to as “Kokai”) H05-295084 and Kokai H07-53870, it was proposed to solve this problem by means of curable epoxy resin compositions that incorporate epoxy-containing organopolysiloxanes. However, the use of such compositions is limited because they produce cured products which either are still rigid, insufficiently flexible, and are subject to warping or cracking, or delaminate and create gaps between themselves and the surfaces of the electronic devices.
On the other hand, Kokai H05-320514 and Kokai 2005-154766 disclose curable silicone compositions comprising curing agents and epoxy-containing organopolysiloxanes. Cured products obtained from such compositions are soft but still have either a high coefficient of thermal expansion, or low strength and low modulus of elasticity. Kokai 2006-306953 discloses a curable silicone composition that contains a thermally conductive filler. However, in order to obtain a cured product of high thermal conductivity, the composition should contain a large amount of thermally conductive metal powder, in particular a silver powder. In addition, a cured product obtained from such a composition has poor adhesive properties.
It is an object of the present invention to provide a curable silicone composition, which possesses excellent handleability and workability in combination with low viscosity and which, when cured, forms a cured body of excellent elasticity, adhesiveness, and thermal conductivity.